1. Field of the Invention
The present invention relates to a multi-stroke punch press designed to operate at an adjustably variable rate of strokes and including a control apparatus provided with a design characteristic curve and which is operative to produce signals depending from the design characteristic curve for an adjusting apparatus which is operative to set the depth of immersion of the punch of the punch press depending from the signals emitted from the control apparatus while the punch press is operating.
The invention further relates to a multi-stroke punch press designed to operate at an adjustably variable rate of strokes and having a control apparatus which is provided with a design characteristic curve and is operative to produce signals depending from the design characteristic curve for an adjusting apparatus which is operative to set the feeding length of the material to be punched depending from the signals emitted from the control apparatus while the punch press is operating.
Changes of parameters in the operation of punch presses, such as rate of strokes, variety of tools or work and type of pieces, always cause deviations from preset design values. For one example, changing the rate of the strokes changes the mass forces change, i.e., the mass forces increase along with an increasing rate of strokes. Such leads to small elastic changes in the dimensions of moving parts of the punch press, changes in the plays or clearances of bearings, and changes of the height of the tool closure and immersion depth of the tools. For another example, various tools which deviate relative to each other in respect of their mass also cause different moments of inertia in operation. These inertias can add themselves to the previously mentioned mass forces or inertias, and accordingly, to further deviations from the preset design values. For another example, particularly with regard to the immersion depth, the characteristics of a work piece to be processed, such as for instance its metallurgical characteristic or the shape of the product to be produced, have an influence.
Deviations from design values occur also in the feeding apparatus where the measure of the length of feed deviates from a respective preset design value, whereby in this instance an increasing number of strokes and the mass of the web being accelerated cause further errors.
2. Description of the Prior Art
The German Patent Specification DE-27 31 084 discloses a punch press in which the immersion depth of the punch or tool can be adjusted while the punch press is in operation via a control apparatus. A design characteristic curve is set in the mentioned control apparatus. The curve shall represents the immersion depth as a function of the number of strokes per minute of the punch press. This characteristic curve is taken as design value. The value of the immersion depth is measured and compared with this design value. In case of a deviation of the actual value, an adjustment towards the design value is produced by such control apparatus.
Practical operation has, however, revealed that such a control does not always lead to satisfactory results. The reason is that the actual values of operation of such a press are subject to complex changes over the entire range of the rate of strokes, which will be explained in detail further below. As a result, the mentioned control apparatus can oftentimes not supply satisfactory results over the entire range of the rate of strokes. This is the more so because of the desire to produce products by punch presses with increasingly higher precision.